The objective of this longitudinal, prospective study is to identify psychological, behavioral, and environmental factors associated with accepting and completing hepatitis B virus (HBV) immunization among patients attending a sexually transmitted disease (STD) clinic located in Chicago, IL. This research will have implications for the design of interventions to increase rates of HBV immunization among these patients, who are at high risk for HBV infection, an STD. The first specific aim is to assess the association of psychosocial and environmental factors to acceptance and completion of HBV immunization. The Health Belief Model will be used to guide the development of predictors of HBV immunization. HBM factors include perceptions of: susceptibility, severity, benefits, and barriers (including environmental barriers). The second aim is to evaluate the association of other health behaviors to acceptance and completion of HBV immunization. The third aim is to evaluate the influence of vaccine characteristics (e.g., cost, mode of delivery, etc.) on decisions to get immunized. During phase one (year one of the proposed plan), focus groups (60 subjects) and individual interviews (20 subjects) will be used to develop a questionnaire based on the HBM, health lifestyle research, and conjoint analysis methodology. An additional 20 interviews will be conducted to evaluate possible reactions to the proposed computer-assisted interview data collection method and to determine the most effective and understandable way to present the study to prospective subjects. Also during the first year, drafts of the questionnaire will be pilot-tested via in-person interviews with 20 subjects and via computer-assisted interviews (with oral and visual presentations of items) with 20 additional subjects. During phase two (years two and three), 1,320 patients (18 years and older) will be recruited from a Chicago STD clinic during routine medical visits. Patient who use the clinic are over 95% African-American and 56% male. Females will be oversampled to ensure a balanced gender distribution. During phase two, the questionnaire will be administered as a computer- assisted interview with both oral and visual presentations of questions. It will cover socio-demographic information, health beliefs, health behaviors (including sexual behaviors), and descriptions of possible vaccine characteristics. After completing the questionnaire, subjects will be offered free HBV immunization, which will require two follow-up appointments to complete the three-dose course. Outcome measures of interest include: (1) acceptance vs. rejection; (2) compliance with two doses vs one dose only; and (3) completion of immunization vs. two doses only. The relationship of socio-demographics, health beliefs, and health behaviors to the outcome measures will be assessed with multiple logistic regression (MLR). The importance of vaccine characteristics in influencing vaccine choice will be evaluated with conjoint analysis, a technique often used in marketing research.